rxjs's Observable and vue's observer mode is not a thing

Observable is a stream, it has many functions. Api will help you understand

you need to have an observable object, and then subscribe to handle some operations of the observable object through the observer.
you can solve this problem through proxy.

let list = [1, 2, 3, 4];
let listProxy = new Proxy(list, {
  set(target, prop, value) {
    if (prop != 'length') {
      // ...
      console.log(`Setting: ${value}`);
    }
    Reflect.set(target, prop, value);
    return true;
  }
});
listProxy.push(5);